The invention relates to disposable garments, and more particularly, a pants-type diaper, which is equipped with elastics strips effectively encircling the leg-holes without traversing the crotch region and to a method for producing such diapers.
Disposable diapers of the children""s training pant type, or of the adult incontinence type, are typically equipped with elastic strands, which encircle the leg-holes. These strands of elastic are typically captured with adhesive between two layers of nonwoven materials. Various methods are used to position these elastic strands so that they produce the desired encircling effect.
In one method of manufacture, the diapers are produced in an orientation whereby product flow is in the form of a single continuous web and the direction of travel is at a right angle with respect to what would be described as the crotch line of the diaper, i.e., the normal direction of product flow is parallel to the waist as opposed to parallel to the crotch.
One method of creating the desired effect of encircling the leg holes of the pant with elastics is to interleave two swaths of elastic strands, each curving across the face of the traveling web, encircling about one half of the leg-hole areas and crossing the path of the other. As a pair, they create a boundary around each leg-hole cutout, which resembles a circle or ellipse. In practice, however, the lateral excursions of the elastic lay-down device are speed-limited. As the traveling web is moving at some speed in one direction, and as the elastic lay-down device has speed and acceleration limits in the cross-direction, there is a limit to the steepness of the oblique angle which it is possible to form between the two. The result of this limitation is usually seen in the form of apparent incompleteness in the formation of the leg-hole-encircling pattern, particularly at the crotch line, where the two swaths cross each other.
From the point on the web at which one leg-hole pattern has been completed to the point at which the next can be begun, the elastic laydown device must reposition itself to a favorable starting point. This period of repositioning occurs as the crotch region passes the laydown device. As a result, the elastic strands must also cross this region of the product, at which they may or may not be attached by means of adhesives to the carrier webs. Various means are used to control or limit the positional relationships of the elastic strands in this region. The two sets of strands may cross over each other, creating an xe2x80x9cxxe2x80x9d pattern, or, they may loop back over to their respective sides, creating an xe2x80x9cOxe2x80x9d at the center of the crotch region. Alternatively, they may be mechanically stopped and prevented from crossing each other, creating two sets of generally parallel lines at the crotch. The laydown pattern used at the crotch will determine the final appearance of the product in this area.
The shirring effect created by elastic strands when laminated with any flexible fabric is well known. However, to have this shirring effect applied to the crotch of a pant-type garment can be undesirable. The elastics create a contractile force, which tends to distort the garment at this location, thereby reducing the garment""s aesthetic appeal, effectiveness and comfort. Thus various methods of reducing or eliminating the effects of the elastic-tension normally occurring at the crotch have been attempted. These methods include the elimination of the adhesive bond between the strands and the liner materials described in U.S. Pat. No. 5,745,922 as xe2x80x9cunsecured spacexe2x80x9d as well as various methods of cutting the strands to eliminate their effects.
While the presence of the leg-hole elastic strands at the crotch region is claimed by some to be of benefit in biasing the diaper""s inner cuffs against the user""s legs see U.S. Pat. No. 5,188,627; Igaue, et al, it is believed by the present applicants that the disadvantages, described above, outweigh any advantages.
As mentioned, one method of eliminating the undesired effects of the elastic strands which cross the crotch region is to sever them. This method is described in U.S. Pat. No. 5,660,657. Unfortunately, such severing usually requires the introduction of a transversely extending cut, which can result in a loss of web tension in the severed part of the carrier web. This also creates an undesirable opening in the diaper backsheet. A proposed solution for this problem is taught in U.S. Pat. No. 5,707,470, wherein an ultrasonic device is used to sever the elastic members, while the carrier webs which encapsulate the elastics are left intact. See, also, U.S. Pat. No. 5,643,396. Another problem associated with such severing lies in the tendency of the unsecured severed ends of elastic to retract to some point beyond the limits of any adhesive pattern. Thus, the elastic strands are not controlled or anchored near the ends of the adhesion pattern and may snap back to further into the adhesive pattern. This results in an incomplete elastic pattern and poor product characteristics.
One method of compensating for the incompleteness of the encircling pattern entails insertion of an additional set of elastic strips, running parallel to the crotch line and transverse to the web path. See U.S. Pat. Nos. 5,634,917 and 5,660,657. Typical products of this type are provided with an outer laminate, which is formed of an inner liner material and an outer backsheet material, between which the leg-hole elastics are disposed.
It is a principal object of this invention to provide an improved method of producing pants type diapers and to provide the resultant improved diapers. A pants-type diaper, is provided which is equipped with leg-hole elastics which effectively encircle the leg-holes without traversing the crotch region.
In accordance with one aspect of the invention, elastic strands are eliminated from the crotch region of a pants type diaper. In accordance with a related aspect, the invention provides a method wherein undesirable elastic material is encapsulated and then an interior longitudinal zone of material which contains the undesirable elastic is cut away and removed. The invention provides for the removal of a strip of inner liner material carrying the undesirable crotch-region strands before the remaining inner liner is combined or laminated with its complementary outer backsheet layer.
In accordance with a further related aspect, the remaining webs, which contain elastic strands, are subsequently laminated with a cover sheet. In a preferred embodiment of the invention, the remaining webs may be rejoined before lamination, thereby reducing the segment of leg opening perimeter which is removed.
In one embodiment, the leg-hole elastic swaths are laid down on an inner nonwoven carrier web, following appropriate curving patterns. The resultant composite web is then longitudinally slit into two narrower webs. The inside edge of each narrower web is then folded longitudinally to cover that part of the elastic pattern which is to be removed. This operation serves to cover the exposed adhesive and to entrap the elastics in this area. The entrapped elastics and the material within which they are enclosed are then removed by again slitting the edge of the webs and scrapping the waste edges. The remaining webs, with their semicircular elastic patterns intact may then be subsequently brought back to positions of contiguity by guiding means. This relocation brings the two semi-circles together to form more nearly perfect elastic circles or ellipses. The two narrower webs are then laminated with an outer carrier web, which entraps the remaining elastic swaths, creating a final laminated outer backsheet for the pant-type diaper. Subsequent processes insert an absorbent chassis or pad, cut out the leg-hole, fold the web longitudinally, and seal and cut the web into individual pants type diapers.
A second embodiment of the invention involves a similar process, but differs, in that instead of folding the slit edge of the web over to cover and entrap the elastics which are to be removed, separate strips of web material are introduced for this purpose. Such web strips may be obtained by slitting them from either the outer or inner edges of two narrow webs.
A third embodiment, a variant of the second embodiment, covers and entraps the elastics with a single, wider strip of material. Such web may be an edge previously cut and removed from the inner liner material or may be separate material provided for this purpose.
A fourth embodiment may be similar to one of the first, second or third embodiments, but differs in that the two narrow webs are not brought together prior to lamination. Instead, the gaps or missing segments between two semi-circles around the leg openings are replaced by elastics provided in the edges of an absorbent chassis or pad, which overlays the crotch area.
In a yet further embodiment of the invention the intermediate narrow strip of material is eliminated. A single web, or if desired, a pair of traveling webs are provided onto each of which an adhesive pattern is applied. The elastic strips are laid down on the adhesive in a serpentine pattern. The strips may be firmly secured to the adhesive by pressing them into the adhesive, for example, by using a pressure roll. A chilled slitting knife may be used in order to minimize adhesive build-up or contamination on the knives. Also, the adhesive can be applied in a pattern which leaves a gap in a strip along which slitting takes place , order to facilitate clean cutting of the composite web. After slitting and removal of the trim, a back sheet is applied which results in the elastic strips being sandwiched between the slit webs and the backsheet.
Briefly, a preferred method of the invention includes the steps of providing a web, defining on the web a portion of a pants type diaper including locations for leg openings and a crotch area therebetween. Then, a layer of adhesive is applied around the leg openings and across the crotch area.
An elastic ribbon is laid down on the adhesive in a semicircular pattern around the leg openings and across the crotch area. Subsequently a narrow web is laid down over the elastic and the adhesive in the crotch area. Then the web is longitudinally slit to sever at least a portion of the narrow web and the unwanted elastic in the crotch area. The removed materials are scrapped, resulting in a pants-type diaper without elastic in the crotch region.
A cover sheet is laminated over the remaining web, and, all material is removed from the leg openings. An absorbent pad is preferably attached over the crotch area. The absorbent pad may optionally be provided with elastic strips adjacent opposite lateral edges which serve to complete the encirclement of the leg openings by elastic material.
The invention, thus, produces a disposable garment including a front body portion, a back body portion and an intermediate crotch portion with spaced left and right leg openings on opposite sides of said crotch portion. The edges of the front and back body portions are joined to form a waist portion, the leg openings each having an upper periphery adjacent to the waist portion and a lower periphery adjacent to the crotch portion. The garment, further, includes a back sheet which forms an outer surface thereof, a top sheet and an absorbent pad positioned in the crotch area. In accordance with the invention, there are front left and right elastic strands which extend, respectively, around a quadrant of each of the leg openings from forward ends which terminate at a forward part of the crotch portion and around the upper periphery of each of the left and right leg openings to the side seam. Similarly, rear left and right elastic strands extend, respectively, around another quadrant of each of the leg openings from rearward ends which terminate at a rearward part of the crotch portion and extend around the upper periphery of each of the left and right leg openings to the side seam. The strands are adhered to the top sheet, and to first and second narrow webs sandwiched between the top sheet and the back sheet. The first narrow web is adhered to the forward ends of each of the left and right elastic strands and the second narrow web is adhered to the rearward ends of each of the left and right elastic strands.
In its most basic form, the invention provides a method of forming pants type diapers which includes the steps of (a) providing a traveling fabric web upon which is defined a portion of a pants type diaper including locations thereon for leg openings and a crotch area therebetween, (b) applying an adhesive pattern on the web around the leg openings, (c) laying down strips of elastic material on the adhesive in an undulating pattern around the leg opening locations on the traveling web and across the crotch area, (d) forming a pair of parallel longitudinal slits along the center of the traveling web to sever the central portion of the web thereby severing the elastic in the crotch area, (e) removing the severed portion of the traveling web and the elastic, laminating a cover sheet over the severed halves of the traveling web, (f) cutting and removing all material from the leg openings, (g) severing the web into individual diaper blanks, (h) folding the blanks in half across the crotch area, and, (i) sealing the edges of the blank together on each side thereof to form a pants-type diaper.
Further objects and advantages of the invention will be apparent from-the following detailed description, the attached claims and the drawings.